Using MySQL FULLTEXT index for Auto-Complete
This information is valid from 7.8.1 on.


Introduction

With Open-Xchange Server v7.8.1 the MySQL FULLTEXT index is supported for retrieving auto-complete results. In order to use that capability an appropriate MySQL version needs to be in place. FULLTEXT indexes are supported starting with MySQL v5.6.4 (see http://dev.mysql.com/doc/refman/5.6/en/fulltext-restrictions.html for details).

Once enabled, an appropriate index is created on the prg_contacts table automatically and is used afterwards to serve the "find as you type" auto-completion requests in a more efficient way.

Moreover using a MySQL FULLTEXT index provides improved results when searching for "tokens". For instance an E-Mail address gets tokenized in the following way:

jane.doe@somewhere.com
yields the tokens: "jane", "doe", "somewhere", and "com"

Thus a user is able to start typing e.g. "somewhere" or "doe" to hit that search result. Without FULLTEXT index support, the user is supposed to enter "jane" to get that hit.

Configuring usage for MySQL FULLTEXT index

For enabling the usage for a MySQL FULLTEXT index the property "com.openexchange.contact.fulltextAutocomplete" needs to be set to "true" and a restart is supposed to be performed. Once set to "true" an appropriate update task (com.openexchange.contact.storage.rdb.groupware.AddFulltextIndexTask) gets executed on next login attempts for associated database schemas.

An administrator can even influence what fields are supposed to be considered for FULLTEXT -backed auto-complete executions by modifying "com.openexchange.contact.fulltextIndexFields" property.

Please Note

As explained above the update task gets only executed once (the time when a first login attempt for an associated database schema happens). In consequence, modifying the "com.openexchange.contact.fulltextIndexFields" property later on has no effect (even a restart does not get the changes applied). In order to apply the changes applied to "com.openexchange.contact.fulltextIndexFields" property, the associated update task is required being re-executed using the "forceupdatetask" command-line tool:

/opt/open-xchange/sbin/forceupdatetask --task com.openexchange.contact.storage.rdb.groupware.AddFulltextIndexTask <other command-line arguments>

Otherwise the FULLTEXT index will stop working.

MySQL configuration options

An administrator may want to change how the MySQL FULLTEXT index works. MySQL only supports to change [word length] and [list] for the InnoDB storage engine.

The MySQL default value for the minimum word length is set to 3. In case users should be allowed to also retrieve results when typing less than 3 characters, the "innodb_ft_min_token_size" needs to be changed accordingly in the MySQL configuration file:

innodb_ft_min_token_size=2

Please Note

Changing any of the MySQL configuration options requires that FULLTEXT indexes are re-created.

Taken from MySQL reference manual:

"...
Rebuilding InnoDB Full-Text Indexes
If you modify full-text variables that affect indexing (<code>innodb_ft_min_token_size, innodb_ft_max_token_size, innodb_ft_server_stopword_table, innodb_ft_user_stopword_table, innodb_ft_enable_stopword, ngram_token_size</code>) you must rebuild your <code>FULLTEXT</code> indexes after making the changes. Modifying the <code>innodb_ft_min_token_size, innodb_ft_max_token_size</code>, or <code>ngram_token_size</code> variables, which cannot be set dynamically, require restarting the server and rebuilding the indexes.

To rebuild the <code>FULLTEXT</code> indexes for an InnoDB table, use <code>ALTER TABLE</code> with the <code>DROP INDEX</code> and <code>ADD INDEX</code> options to drop and re-create each index.
..."

Thus an administrator may manually drop and re-add the index or simply re-execute the associated update task (com.openexchange.contact.storage.rdb.groupware.AddFulltextIndexTask) as explained above using "forceupdatetask" command-line tool.